Plant Cover Crops

Learning about the benefits of planting cover crops.

nutrient management

Advancing Cover Crop Adoptions Research Agenda

Advancing Cover Crop Adoptions Research Agenda

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Will corn planted after cover crops consistently out-yield corn planted without cover crops? Research has shown some nice advantage in areas. More research should give farmers more confidence in cover cropping.

Sarah Carlson, Midwest Cover Crop Research Coordinator with  Practical Farmers of Iowa and Ryan Stockwell, Agriculture Program
Manager with the National Wildlife Federation have written an agenda that will help researching cover crops be more scientific over the next six to eight years.   The research agenda is published in the Journal of Agriculture, Food Systems, and Community Development
ISSN: 2152-0801 online www.agdevjournal.com

Here is the abstract of this aggressive agenda:

Copyright © 2013 by New Leaf Associates, Inc.
Abstract
Given certain ecologic and agronomic characteristics of conventional corn and soybean monocultures, cropping systems reliant solely on these two commodities inevitably lose soil and nutrients.  Leaky cropping systems not only hamper society with negative externalities, but also erode the very natural resources needed to produce food and sustain civilization. The United States Department of Agriculture (USDA), state agriculture department staff, farmer organizations, agribusiness leaders, and conservation and environmental organizations now see cover crops as a solution to reduce the negative externalities of conventional row-crop agriculture. Farmers are asking for increased agronomic and economic research to help them understand the benefits of and implement the use of cover crops. Researchers for the most part are not keeping up with farmers’ innovations on cover crops nor on providing the information sought by farmers. This article outlines the questions farmers are asking about cover crops and provides suggestions to agronomists, soil scientists, and researchers on research topics to best answer those questions. Additionally, social scientists must initiate a new round of research to understand the underlying concerns farmers have with cover crops and help to define the information (both content and source) that best informs and influences farmers. This article outlines specific issues and questions social scientists can research to contribute to the advancement of more sustainable farming practices and, in particular, cover crops.

Keywords
adoption, climate change, cover crops, diversity, externalities, innovation, natural resources, nutrient loss, resilience

You can find the complete paper here.

 

Fall Cover Crop Management

While in southern Minnesota in early September 2013 I was asked when a farmer should plow his cover crop field this fall because he needs the fields to be “black” this winter in preparation for next spring.  I shuddered.  There I was in a beautiful field of cover crops that are jump-starting some biology on a “biologically dead” field and the farmer wants to kill his biology driving mechanism.  UG!  The main reason he wanted to till the field was to have warmer soils in the spring where he had black soil.  I shared that our research sowed much different results.  His thought process sound right but has proven to be a myth, not a fact.

A beautiful stand of Oats, Berseem Clover, and Pasja Hybrid Brassica on prevent plant acres in SO. MN
A beautiful stand of Oats, Berseem Clover, and Pasja Hybrid Brassica on prevent plant acres in SO. MN

I told the farmer to leave the cover crops in all winter and use conservation tillage next spring.  (He’s not a no-tiller.)  We dug some shallow root pits for a field day and we found many problems that I believe can be somewhat rectified if the cover crops are left in all winter.

We found many soil health problems in this prevent plant field

  • Severe compaction– many areas had compaction starting at 2-3″ deep.  Part of that was from spring tillage of wet soils…but the compaction was about 8″ thick as the soil was coming up in blocks the size of cinder blocks!
  • Lack of soil biology – I know this because we found a significant amount of corn fodder 2 foot deep that was not even breaking down.  It would have been buried with the deep ripper 18 months ago.  I could not believe my eyes!
  • Lack of aeration in the soil – the soil was literally rock hard.  We did find a few earthworm channels but it was so dry that worms were small and deep.
  • Low organic matter – I’m not sure how low it was but there was very little soil structure.  I talked with a regional NRCS employee and the local SWCD specialist and both men lamented that many of the soils in that region were “about as bad as this one”.
We found corn fodder two feet deep that had not yet decompose after over 18 months.
We found corn fodder two feet deep that had not yet decompose after over 18 months.

I need to be fair.  The farmer currently renting this field has only farmed it a few years and he is making major strides to improve this farm.  But he has lots to accomplish before he has a healthy field.  Having cover crops are a great first step and he knows it.

Other solutions (instead of cover crops) being proposed to fix the “tight” soils (“unhealthy” soils) in the region

  • Tile – LOTS and LOTS of tile has been installed in prevent plant acres this year.  Farmers know they need aeration and percolation in their “tight” soils.  The regional specialist from NRCS lamented that many farmers don’t believe that cover crops are a solution to make their soils better long term.  Tile is not bad; but tile and cover crops are a much better solution.
  • Deep ripping – this will get air into the soil and break up compaction, but will it build soil health?  No, it will not  (note the corn fodder found 2 foot deep in a root pit).  Let cover crops naturally deep rip the soil.
  • Tillage- and lots of it – many fields in the area had been tilled (disked, field cultivated, etc…) four times already to control weeds…Unfortunately it also reduces organic matter and soil structure and soil health.

So what should happen with the cover crops heading into winter?

  • Leave the cover crop growing into the winter – This will give the best opportunity to help with aeration and percolation.  This also helps build soil structure and reduce compaction.  (See deep ripping, and tiling above…just let the cover crops do this naturally!)
  • Sarah Carlson from Practical Farmers of Iowa recently wrote an article about this topic and you can find it here Prevent Plant, Cover Crops, Now What 2013.
  • Let the cover crops keep putting down deep roots – we found roots of crimson clover, radishes, cereal rye, annual ryegrass, oats, and Pasja all around 24″ deep.  Let them keep growing deeper to open up the soil to get air and moisture deeply into the soil profile.
This 5 week old PileDriver Radish shows the compaction zone starts at around 2-3" seep. Roots on this radish went over 24" deep despite very dry conditions.
This 5 week old PileDriver Radish shows the compaction zone starts at around 2-3″ seep. Roots on this radish went over 24″ deep despite very dry conditions.
This field had very poor soil structure. The regional NRCS specialist told me that many fields in the area had similar issues
This field had very poor soil structure. The regional NRCS specialist told me that many fields in the area had similar issues

Fertilizing Cover Crops & Planting Legumes After Soybeans

If you spend any time at all in cover crop meetings, you may have heard that it’s a good idea to add 20-50# of Nitrogen per acre to your cover crop – if you don’t have a legume in the mix or you don’t have manure available. You also probably heard (or participated in) the grumbling that predictably starts from the crowd. Who wants to fertilize a crop that they will not harvest?

While it’s true that producers will not “harvest” the cover crops, they will have healthier cover crops which should lead to healthier soils and healthier profits.

Manure as the No-Brainer

Obviously if manure is available it is a smart move to put manure where you will have or already have cover crops.  We know from research that cover crops can hold as much as 90% of the nutrients from manure applications.

We have also know that where manure is applied without a cover crop being present (even if worked in) we can lose a significant amount of nutrients into ground water or as surface run-off.

What About Adding Commercial Fertilizer?

The Radishes on the left had manure applied and those on the right did not have any additional nitrogen applied.
The Radishes on the left had manure applied and those on the right did not have any additional nitrogen applied.

But, what if there is no manure to apply and for some reason you do not want to include a legume in your system?

Is it worth applying 50# of nitrogen to produce a cover crop?

Let’s look at what we think we know:

  • Pages 22-24 of Managing Cover Crops Profitably provide formulas to figure out the value of using cover crops as a green manure in a cover crop system –  whether with legumes, manure, or fertilized.

Look especially at the section on “Potential losses” to see that there can be nitrogen losses even in this scenario.

  • Cover crop experts say to count on 50% of the N captured or N produced by a cover crop to be available to the next cash crop.
  • It appears that adding a grass with legumes or brassicas will help “slow down” the release of the N in the spring making it more slowly released to the next crop.

 

Here is a photo of the Ingham County Michigan Cover Crop Plot. Where there was a legume in the mixture there was considerably more growth and earthworm activity
Here is a photo of the Ingham County Michigan Cover Crop Plot. Where there was a legume in the mixture there was considerably more growth and earthworm activity

What can we expect if we plant a cover crop and we don’t add more nitrogen?

How will that cover crop do?

I will utilize work that Dan Hudson did when he was an Extension educator in Ingham County Michigan in cover crop plots he planted back three or four years ago.

  • Radish tubers are considerably smaller and the roots appear to not be as deep  (I have not dug a root pit in this scenario).
  • Grasses have a more shallow root system in forage settings when fertility is lacking.
  • The cover crops were pale green.
  • The “hungry” grass cover crops had less earthworm activity than in the grass + legume mix plots.
  • “Hungry” radishes and turnips had much less tuber and top growth, thus sequestering less nutrients (one of their main functions).
  • Winterhardiness on cover crops is potentially not as good when the cover crop is undernourished.

What can we expect after soybeans?

Do we need a legume in the cover crop mix following the beans or is having a grass and/or brassica to sequester the N from the soybeans good enough?

Let’s investigate the difference between adding a legume to a cover crop mix following soybeans compared to planting scavengers only.  The charts are from our family farm trials.  The charts show the chlorophyll readings of the corn in the year following the soybeans (and then following a cover crop).

It is important to look at the “Y” axis as each chart is slightly different in how it shows the top reading.

When Austrian Winter Peas were added to a scavenger (Radishes) the chlorophyll readings were very favorable compared to the no cover crop check plot and plots with just scavengers.
When Austrian Winter Peas were added to a scavenger (Radishes) the chlorophyll readings were very favorable compared to the no cover crop check plot and plots with just scavengers.
Just like the peas gave us an advantage over the no cover crop check the crimson clover showed very favorably.
Just like the peas gave us an advantage over the no cover crop check  and scavengers, the crimson clover also showed very favorably.

 

While the Oats and Radish showed exceptionally favorable in the early part of the season the plot are "ran out of gas" as the corn was pollinating.
While the Oats and Radish showed exceptionally favorable in the early part of the season the plot “ran out of gas” as the season progressed.
Straight Winter Cereal Rye was impressive early season but also did not fare as well against the check as the mixes with legumes
Straight Winter Cereal Rye was impressive early season but also did not fare as well against the check as the mixes with legumes.

As we looked at the yield of the corn in these plots we saw a considerable difference – suggesting that even after soybeans we might want to add a legume to improve the corn yield the following year.

Yields from the different cover crop plots shown above were:

Check Plot                                    105.24 bu/ac

Winter Cereal Rye                      126.86 bu/ac

Oats and Radish                          138.79 bu/ac

Crimson Clover + Radish           153.99 bu/ac

AW Peas + Radish                        164.82 bu/ac

Conclusion

All indicators seem to point that adding manure, a legume, or additional N might very well pay off when planting a cover crop, even after soybeans.  However, adding a nitrogen source is not necessarily vital to having a successful cover crop system.  I would suggest that you try different scenarios on your own farm and in your own system and see what works best for you.

Cover Crops Increase Iowa Corn Yields

Cover crops are helping to increase yields in Iowa corn fields.  My friend Sarah Carlson from Practical Farmers of Iowa sent me the following testimonial from Eric Franzenburg from east central Iowa (about 1.5 hours east of Ames).

Eric Franzenburg has seen increased corn yields of 20-40 bushels per acre the past 3-4 years after using cover crops!

Thanks to Sarah and Eric for making this testimonial public.  I know that there are many other farmers that have seen similar results.  If you have and would like to share with the readers of plantcovercrops.com I’d greatly appreciate it!

Eric’s testimony:

I believe that the researcher from the article is on to something in regard to relieving drought stress (research I proposed on this blog).

I went out to do some yield checks on our conventional corn fields about a week ago to get an idea where we were.  One of the fields was seeded with fall rye earlier in the fall (September 1, 2011), followed by 3,000 gallons/A of hog manure (later in the fall). This spring we killed the rye with Roundup when the rye was over knee high, waited over 2 weeks to plant, tilled one pass with tandem disk-harrow, and planted later in May. It was the last field I planted.

I followed with a sidedress of 70 lbs at V6. This field will out-yield all other fields by 40 bpa.  The plant health is excellent, and I was telling Sarah that if you start poking around looking for rye residue it is virtually gone (not sure if this is good or bad).

We have been doing this same program for 4 years now and I am no longer worried about planting corn the third week of May under these conditions, especially after this year; this has been a very telling growing season. We are coming up with the same results 3 of the 4 years (yields 20-40 bu. higher).

I have been wondering what the mechanisms in the soil are that have given us these results.  While the scenario that the researcher has proposed sounds good, it does not sound like much work has been done to prove this out.

Planting into “Out of Control” Peas – The Rest of the Story

In September 2011 I posted about an Ohio farmer that planted into “out of control” peas and shared about his story of how the field was looking pre-harvest.  I have recently visited with Dave (the producer) and he shared the information that a number of you asked for…and also surprising yield data. Dave farms with his father-in-law Ron in Mercer County, Ohio near Rockford (NW Ohio).

Sometimes it takes courage to farm with cover crops! Dave and his father-in-law Ron planted with confidence as the ground was "very mellow" compared to other ground without a cover crop.

Here are Dave’s observations and the 2010-2011 field history:

  • Hog Manure applied late summer of 2010 – 5000 gal/ac
  • No other fall fertilizer
  • N-Vest Groundbreaker Mix (Austrian Winter Peas and GroundHog Radish) planted Labor Day weekend 2010

Peas that survived – and other weeds, wheat, clover, etc. – were sprayed (after a wet, wet spring) on June 2, 2011.

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Herbicide/Insecticide Mix: (rates per acre)
20 gal Water
Alliance – .2 gal   (1 gal/100 gal water)
Roundup WeatherMax – 44oz
Weedone 650 – 1pt
PowerLock Surfactant – 6oz
Baythroid (insecticide) – 2oz

Corn was planted on June 3, 2011.

Additional Fertilizer applied (in addition to nutrients from manure and N from peas)

20 gal/ac 10-34-0 starter fertilizer with 1qt/ac zinc

40 gal/ac 28-0-0 side dress with Agrotain N stabilizer

Results

Even though several acres in the area were too wet to plant this field of peas was in great shape as you can see the row closed "perfectly" behind the planter.

Weigh wagon test showed 215 bu dry yield.  Dave guesses the whole field average was between 200-215 dry (he has no scales at home to check weight of entire crop).
Dave also thinks that the yield was 10-15 bu better that most of their other corn (w/o manure and w/o cover crops).

The seed placement of this no-till planting into the peas was "near-perfect".

All things considered…the wettest spring in Eastern Corn Belt History, late planting date, planting into 3+ foot tall peas, < 1″ of rain in the month of July (with 22 days 90 degrees or more), a wet fall that delayed harvest..and the result was over  200 bushels/acre.  I’d take that everyday for that part of Ohio, and so will Dave and his father-in-law Ron.

The roots on the peas were massive by early June. Don't expect this in most years but this certainly did not hinder planting, getting a good stand, or attaining a very high yield!

Other observations from Dave:

Positives:

Better soil structure

Deeper root penetration by corn roots

Great seedbed to plant into

Great soil cover after cover crop was killed

Better water retention thru the dry months

Nutrients saved from hog manure

Negatives:

Too much growth in wet spring

Took a lot of time to plant due to pea growth

 

Thanks Dave for sharing your story!